You Want Me To Do What?
by Dr. ForgottenFables
Summary: After finding out that he was the Son of Satan and being made to hide in plan sight in an exorcist classroom, Rin thought his life couldn't get anymore complicated. But when his new familiar starts to feel the heat, he realizes he should have read up more on 'Cait Sith'. Now with the True Cross Order pressuring him to do the deed, what is a half demon to do?.. Other than that cat.
1. Chapter 1

**I own nothing, not the characters, the space where this story exists, or even the eyes that you are using to read it. This is for entertainment purposes only, no money involved.**

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~Cait Sith~

 _A majority of legends of the Cait Sith originate from Scotland, but that is not to say that is their only habitat, as the Cait Sith can possess any cat anywhere in the world._

 _Cait Sith originated from a failed summoning ritual of early western witches that resulted in them being bonded with their familiars. Because of this, all Cait Sith are female and may transform between their normal catlike state, and the form of a woman. Thought the number of times they can undergo this transformation is limited to eight times. After that the Cait Sith is stuck as a cat forever. This is the origin of the saying 'cats have nine lives'._

 _Since the Cait Sith are more venerable when they are in their human forms, they usually only leave the catlike forms when they have found what they believe to be a strong potential mate. After finding this mate they will assume their human forms in order to have children, and will not return to their catlike form until after they had given birth..._

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"Oh no..." Rin grumbled as he looked over from his demonology textbook to his bed were his Cait Sith familiar, Kuro, who he had always assumed was a boy, was tangled up in the blankets, looking to the world like a cheerful high school girl with short black hair that framed a smiling face with sharper than normal teeth and faint whisker like marks. Kuro's small yellow horns stook out through her black hair but looked more like a hair ornament rather than the real thing.

She had a fairly modest chest that was the halfway mark between Izumo's and Shiemi's and her long cat's tails was swinging back and further through the air as blushed underneath Rin's stare and her smooth peachy skin, slightly turning her bright green eyes away from him.

Oh, and they didn't have any clothes for him.

"Well Nii-san. As her tamer, you have to take responsibility." Yukio said patting his older brother on the shoulder.

"Wha..?" Was all Rin could say. The hidden son of Satan didn't know what else to say.

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 **I've need done anything like this before. But after I read up a bit on Cait Sithes, I just thought it would be funny.**

 **This will be the first time I will intentionally try for romance. Could also be the last time. Most of my normal readers already know I'm not very good at it.**


	2. Chapter 2

**I own nothing, not the characters, the space where this story exists, or even the eyes that you are using to read it. This is for entertainment purposes only, no money involved.**

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"Here you go. One of my Rin special fried rice stuffed omelettes." Rin said as he placed the plate full of food in front of the newly humanified Kuro. The Okumura brothers had contacted Mephisto who for some reason had clothes that would fit the girl.

So now she was dressed in cat themed pajamas, with a white top with a picture of a anime cat on it with the word 'Neko' right underneath it, and pink bottoms that were covered in pictures of various cats from various animes and mangas. Her tails sticking out and swinging side to side as she stared at the food with hungry eyes.

"Thanks for the meal!" She said before burying her face into the food.

"Guess we need to teacher her table manners." Rin said as he sat down across from the girl. The act of cooking had calmed down Rin to the point were he was open to asking questions. "So what are we supposed to do about this?" He asked as he ran a hand through his messy raven hair to push it out of his electric blue eyes. He glanced over at Yukio and Mephisto who were both seated at the table and had what Rin could have sworn were pleased expressions on their faces. Something that was ticking him off.

"Well I suppose we should first enroll her in all of your classes, since she will need to be close to you at all times..." Mephisto said. Older demon had a huge smile over his pale face. The top hatted clown of a demon/exorcist was enjoying every minute of it.

"What!? We can't do that? She's a demon." Rin said in a panic. "Won't the exorcists try to... you know."

"Nii-san, she was always a demon. And she is still your familiar. So no one is going to try to hurt her." Yukio said inwardly laughing at his brother's overly protective reaction. Rin's younger twin brother was a little taller than him with dark brown hair, slightly darker blue eyes and a few moles dotting his face behind his glasses.

"On the contrary, the Order will be overjoyed to hear that Kuro-chan has chosen a human mate." Mephisto said in his grandiose manner, further confusing Rin.

"What are you talking about? Why would they want more half demons?" Rin asked confused. He thought him being a half demon was a bad thing.

"Nii-san, half demons are considered a blessing to the Order, as they provide generations of children who are superior exorcists, like the other students in the cram school. Most of them have a family tie to a powerful demon if you trace back there lineage far enough. It is what gives people like Shiemi and Kamiki-san their ability to summon demons, and helps Arias with the strength of there Sutra chants." Yukio said to his brother. "The only problem with you is that you are related to Satan. If it wasn't for that, you would probably be treated like high nobility by the Order."

"Are you for real!?" Rin asked in wide eyed shock.

"And with a demon as powerful as a Cait Sith, the order would definitely wish to have any many children of such a union as possible." Mephisto added with his demon's smile. "So you better get snapping."

Rin was going to object to being treated like a stud horse but was cut off when Kuro grabbed him from behind. "Rin... can I have some more?" She pouted holding out the empty plate as her breast pressed up against Rin's back.

The half demon swallowed hard. "Um... sure Kuro...chan." he said as he went to prepare another helping for his familiar. The demon catgirl purring loudly at his side as she sniffed in the smell of the food cooking. "So... you really want to... you know... with me..." Rin said turning the color of a ripe tomato.

"Of course I do, Rin. I won't have transformed if I hadn't." Kuro said proudly, giving Rin a cute smile.

"I'm afraid it is completely out of your hands, Rin-kun." Mephisto said as he stood up and began to spin his patchwork umbrella around on one finger. "As an exorcist you will be called to do your duty to the Order. And besides, she's an adorable neko. You should consider yourself lucky." Mephisto said before waving goodbye and disappearing into a puff of smoke.

"What am I going to tell Shiemi?" Rin moped. Sure she had never seen him as more than a 'friend', actually he was probably so fair into the friend zone that he was breaking new grounds in a lost cause. But that didn't mean it wouldn't still be weird that he was suddenly engaged to his cat by order of the church. There were so many things wrong with this that Rin couldn't even keep track of them all.

He nearly jumped as Kuro wrapped herself around Rin's arm and looked up at him with a pout. "Why are you talking about her? Am I not good enough for you?" She asked, her lower lip quivering tears coming to her eyes. Rin's Adam's apple bobbed as he struggled with his inner demons. She was really cute.

"No! Its nothing like that, its just... um... All happening so quickly." Rin said, not wanting to see the girl cry. He had never been very good with dealing with people while they were crying. Didn't matter if it was a demon or a human, an adult or a child, he always freaked out when the waterworks started. "You're good enough, more than good enough, you're really cute, so please don't cry!" Rin said starting to sweat.

"Ok!" Kuro said before she buried her head and his shirt and began to purr again.

"Well its a good thing that we have that settled. Now I need to go and add her to the student roster. Oh, and I'll move my stuff out of our room and to a room... lets say three doors down. That way you won't disturb me when you two have sex." Yukio said, somehow managing to keep a straight face.

"Yukio..." Rin said in horror as he turned from tomato red to a dark crimson. "Aren't you supposed to say to wait until after high school or something." He hissed.

"Why would I say that? The entire point if for her to become pregnant with your children." Yukio said looking at Rin like he was an idiot. "Besides, since she just turned into her human form today, it will be another three years before her first period. She won't be able to get pregnant until after you are done with high school. So no worries. Do whatever you like. It would make our late father very happy." Yukio said as he walked out of the room. The moment the dorm cafeteria door was closed, Rin could hear laughter coming from outside.

"Yukio..." Rin growled angrily as he took Kuro's second helping off the stove. Kuro was about to dig in face first when Rin stopped her and handed her a spoon.

Rin watched her eating his cooking with a big grin on her face and Rin felt happy. She had such a cute smile. But it all seemed so strange, like beastiality. But... she really was cute. And hey, three years. He had time to warm up to the idea.

For right now, the world didn't seem all that bad.

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Down in Gehenna Satan found a package on the door mat of his summer home by the golf course. " **Hm... what's this?** " He mumbled as he lifted up the package and incinerated the envelope that held the attached letter. The paper inside was covered in pink stickers and small pictures of dogs, so Satan knew it came from his son, Samael, the King of Time, also known as Mephisto by the humans.

 _'Dear Father;_

 _I am writing to inform you that our little boy, Okumura Rin, has been chosen by a Cait Sith to be her mate._

 _I thought you should know and I assure you that I will tape the who wedding and send you a copy if you haven't managed to take over Assiah in time for it. She is a powerful young demon and will make you the perfect grandchildren._

 _Now, I'm off to go stir up some more trouble for that spy that the Vatican has sent to keep an eye on me. Its so much fun to play with her. Especially when she gets drunk on duty._

 _Your second son, Samael._

 _P.S. I've included in the package some pictures of the demon that is to be your daughter in law, as well as the full box set of 'Cat Planet Cutes'. I know how much you like ecchi scifi animes. And 'Code Breaker', a show I think you will quite enjoy.'_

" **Oh hell ya!** " Satan shouted, burning the paper off the package and taking it back inside to his DVD player. " **God bless moe.** " The devil said as he flopped down on his coach. This is why Samael was his favorite.

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 **... So yeah, I'm pretty sure my in experience with writing romance is showing. So if you have any suggestions I'd love to hear them.**

 **I like the idea of Yukio being straight faced through the whole thing. Its funnier that way.**


	3. Chapter 3

**I own nothing, not the characters, the space where this story exists, or even the eyes that you are using to read it. This is for entertainment purposes only, no money involved.**

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"Everyone settle down." Yukio said as he took in front of the cram school class, a clipboard in his hand and his usual unbreakable look of professionalism. "Alright class, we are going to be having a new student joining us from now on. I hope you will all be very welcoming to her since the is a new experience for her. You can come in now."

The cram school students watched only have interested as the door opened, but they all took a lot more notices when Kuro actually did walk into the classroom. Even Yamada and Takara, the mysterious students that never reacted to anything went slack jawed as they stared at the girl.

"Hi! I'm Fujimoto Kuro, and I'm looking forward to spending time with all of you! Please take good care of me!" She said happily, even giving a little bow. Kuro was dressed in the True Cross Academy Uniform of a white blouse and a short pink skirt with her tails sticking out behind her, moving back and forth through the air as she smiled at the classroom. Since she didn't like the feel on socks or shoes on her feet she was completely bare foot, showing slightly pointier than usual toe nails.

"As you have all probably noticed already, Fujimoto-chan is a demon. More specifically a 'Cait Sith'. She is Okumura-kun's familiar and has chosen him as her mate. So she will be joining our class in order to stay close to her chosen mate. I hope you will all be very cooperative with this." Yukio said looking over the shocked faces in the room, as well as his brother's bright red face.

But eventually the entire class answered at once with the exact same all telling phrase. "Eh!?"

"Okumura! When the hell did that happen!" Suguro demanded. Though he was an honors student, Suguro Ryuji, also known as Bon by his closes friends, looked like a punk. He was of large build and had wild brown hair with a blond strip dyed down the middle that made his head look a bit like the rare end of a chicken. Suguro was always yelling and had a permanent glare on his face, but he wasn't really that bad of a guy.

"You lucky bastard... I hate you." Shima said, crying to himself. Renzo Shima was the class pervert, he walked around in casual clothes and was always trying to pick up any girl he met. Like Bon, he had dyed his hair, though he had chosen a shade of pink that would stand out to any girl that saw him.

"Shima-san, you need to get over all of these Earthly desires?" Konekomaru said. The last of the three boys from Tokyo, Konekomaru was short, bald, and had large glasses, but still managed to get more dates than Shima.

"Don't give me that." Shima said miserably.

"Rin...-kun..." Shiemi said confused as Kuro jumped over the desk that Rin and her shared and sat between the two of them grabbing onto Rin's arm and pressing her head against his shoulder while purring all the while. Rin rubbed the back of his head with his free arm, giving the same over the top smile that he always gave when someone asked him a difficult question. Shiemi was a usually soft spoken girl with shoulder length blond hair and blue eyes. She had always gone around dressed in a pink and blue Kimono, and was rather ditzy. But this was too much to go unquestioned, even by her.

"Now that we have that out of the way, lets get back to class. Fujimoto-chan, you can share books with Okumura-kun until we get you some of your own." Yukio said before turning to the chalk board and starting to write. "So last class we were discussing the various uses of mistletoe against fall gods. There are countless examples of this in myths going bad to..."

In a true reverse of normal reality, only Rin was paying attention to the lecture material. Everyone else was staring at the catgirl who had snuggled up to the class's lovable dimwit and was purring loudly as her tails moved hypnotically back and forth through the air. Rin trying his absolute best to pay attention to Yukio's class, in an attempt to fight down his inner demons that were becoming aroused by the cat's play.

Shiemi in particular was rather distressed. The entire time she had known Rin, she had thought of him as a friend. But he was more than that. He was her only true friend. Someone who laughed with her, and tried to cheer her up. He was the one who was always watching out for her and protecting her, whether it was from demons or just the name calling of the other students. And he was what had motivated her to try to live her own life and got her out of her slump after her grandmother died.

Even though she had only had a crush on Rin's twin brother, Yukio, she couldn't really say that Yukio was as close a friend to her as Rin was. Yukio rarely ever showed his emotions and wasn't ever open with her, only talking to her the way a teacher talks to their students. Her friendship with Rin had been much closer, even if they hadn't known each other as long.

And even though they were still the same distances from each other, sitting on the same bench, in the same class, it still felt like a large rift had been put between them. Like Kuro was a giant wall that she would never be able to pass.

Shiemi tried her best to look forward and ignore the large lump forming in her stomach. She could taste the emotion that was causing it. It was fear. She was afraid that she was going to lose her only close friend. And that made it hard for her to concentrate. Even though Yukio's class was her absolute favorite, that day she didn't hear a word. The young tamer girl was just too distressed.

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They were back in the gym class, the same as they did almost everyday, running from the Leapers, high ranking lesser demons that possessed frogs, turning them into massive creatures the size of a monster truck with huge teeth. Though in truth they were fairly none aggressive creatures and rather slow for their size. The students were required to run around the pit dodging the Leapers, as the Leapers tried to caught them.

Currently Rin and Yamada were the ones doing the exercise, leaving the others sitting on the top of the pit watching them.

"Keep it up, Rin!" Kuro was shouting encouragingly as her master and mate used the tactic of simply trucking it to evade the demon's hops.

"Hey, Fujimoto-chan..." Shima started talking to the catgirl.

Kuro turned to him and grinned. "Just call me Kuro. It was the name Shiro gave me." She said proudly. Everyone around them was listening in intently as the demon talked.

"Alright Kuro-chan. Um... I don't know how to put this but... why would you want to be Okumura's girlfriend?" Shima asked, rather bluntly.

"Why won't I?" Kuro said tilting her head in a adorable manner.

"How about you just start from the beginning and tell us why you picked him." Izumo said from behind Shima. Everyone was surprised to find that she was at all interested. She didn't seem like the gossiping type. They didn't notice that her eyes were always on the cute ears or the tails that flicked about.

Izumo was a rather short tempered girl, as well as short in general. She had long black hair that she usually wore in ponytails and her eyebrows had a rather odd oval shape, earning her a few nicknames that Rin had intended to be nice, but were rather embarrassing. But one of the things her classmates didn't know about her, was that she was a serious cat lover. But having grown up in a house filled with the spirits of dead canines, she had never been able to have one. So her curiously about Kuro was on overload.

"Well... It started after my last master, Fujimoto Shiro, died." Kuro said looking down sadly.

"Fugimoto Shiro, as in... the Paladin?" Suguro murmured, a bit surprised that she had been the familiar of such an important figure.

"Yeah, Shiro was amazing." Kuro said with a sad smile. "But after I found out Shiro had died... I was really sad. I might have on a little out of control, and hurt a few people when I had found out. I just didn't want to believe them at the time." Kuro watched Rin moving along the outer wall of the pit, trying to get the demon to smash its head on the wall. "They sent exorcists to put me down.

All of the students froze up a little. It wasn't exactly a good light for exorcists to be put it. "But Rin stopped them. He helped me come to terms with Shiro's passing, and stayed with me while I cried to comfort me. He was strong and cool." She said and they all saw a blush creeping up onto her face. "After that I became his familiar and in the few days after that I realized I had fallen for him. So I took on my human form to be with him."

Shiemi thought back to her own first time meeting Rin. It was strikingly similar to the demon girls, were Rin had helped her come to terms with her grandmother's death and helped her move on.

"Rin is amazing. He's kind, strong, fun to play with, and he's an amazing cook." The catgirl said with a wide smile. "He's an ideal mate."

"He... he really is." Shiemi mumbled, too softly for anyone to here her. She felt so stupid. She had been obsessing over Yukio's brand of perfection; tall, dark, handsome, strong, smart, well mannered. She hadn't even realized that Rin was so much more human and fun to be with. And now... he was spoken for. She was starting to see how good of a person he was. But it was all too little... too late.

Rin's turn in the pit had ended and he climbed out just before Yamada. "Hey, Suguro, Konekomaru! You're up!" He said as he got back, like always he didn't seem to be sweating at all, even though most people would have sweated up a storm from the amount of running he did.

"Rin! You did great! I wish we had got to go down there together!" Kuro said as she jumped onto her chosen mate. Shiemi watching all the while, looking a bit crest fallen. Though no one seemed to notice. That is, except for Izumo. The other tamer girl put on her very fox like smile as she realized what was going on. She was going to have a lot of fun with this.

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 **I'm choosing to accept the relative silence I am getting to mean that yes, I am bad at this genre, or that no one cares about it. Though I doubt it is the second one. Though it could be that people only read yaio (or however that is spelled).**

 **If there is stuff I am doing wrong in this story, I am all ears. Flamers welcome, as long as you are funny or your criticism is productive. Otherwise you just aren't very good at flaming, are you?**


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